Organic Chemistry
7 marks · EasyAnswer all parts about alkanes and alkenes.
State the general formula for alkanes.
Name the hydrocarbon with the formula C4H10 and state if it is an alkane or an alkene.
The hydrocarbon C3H6 can be drawn as a straight chain with a double bond. Write its name and draw its displayed formula.
Explain the main difference between alkanes and alkenes in terms of their bonding.
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(a) CnH2n+2
(b) Butane, alkane
(c) propene, displayed formula with C=C double bond in 3-carbons · must show correct double bond between two carbons, correct number of hydrogens
(d) Alkanes have only single C–C bonds (saturated); alkenes have a C=C double bond (unsaturated).
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Marking points
B1 (a) · 1 mark · States correct general formula for alkanes (CnH2n+2)
B1 (b) · 1 mark · Names C4H10 as butane
B1 (b) · 1 mark · States that butane is an alkane
B1 (c) · 1 mark · Names C3H6 as propene
D1 (c) · 1 mark · Draws correct displayed formula for propene with C=C double bond and correct number of hydrogens
B1 (d) · 1 mark · States that alkanes have only single bonds or are saturated
B1 (d) · 1 mark · States that alkenes have a carbon-carbon double bond or are unsaturated
Worked solution
a) The general formula for alkanes is CnH2n+2.
b) C4H10 is butane. It is an alkane.
c) The formula C3H6 is propene. Its displayed formula is:
d) Alkanes are hydrocarbons with only single C–C bonds (they are saturated). Alkenes have at least one C=C double bond (they are unsaturated).